The invention relates to a method and system for computer aided manufacturing measurement (CAM2) analysis. In particular, the instant invention assists in managing large computer-aided design (CAD) files and to the reorganization of the data from those large CAD files into smaller more manageable and quickly accessible files. Further, the instant invention provides for improved CAD model surface selection when comparing manufactured assembly surfaces to the CAD model.
The manufacturing/industrial marketplace commonly uses computer-aided design (CAD) and computer-aided manufacturing (CAM). CAD software allowed engineers to produce 3-D images in the front end of the design process, which shortened the production cycle and led to tremendous gains in productivity. CAM software and equipment increased the efficiency and quality of machined parts. Despite these technological advances in design and manufacturing, something important was missing from the production cycle. That is, a highly accurate, efficient, and convenient measurement methodology for ensuring that the products and components met the original CAD specifications. Historically, measuring assemblies made of numerous parts against the CAD model has been unwieldy, expensive and unreliable.
Traditionally, the measurement and quality inspection function in the manufacturing process has been time-consuming and limited in size, scope, and effectiveness for a number of reasons. Manual measurement tools, such as calipers and scales may be slow, imprecise, and always one-dimensional. Analog test fixtures are costly and inflexible. Also, standard coordinate measurement machines, while providing a high degree of precision, are generally located in quality control labs or inspection facilities at a distance from the manufacturing floor. Parts must be removed one at a time and transported to the lab for components—which often translates into significant “down time” for the production line. In essence, traditional measurement techniques—also known as metrology—have lagged far behind in the technological advances of the production process.
The CAD/CAM and metrology markets, as well as a worldwide emphasis on quality in all aspects of the manufacturing process, are driving the need for a missing link, which is referred to as Computer-Aided Manufacturing Measurement (CAM2). In other words, CAM2 is a CAD-based total quality assurance technology. To date, adaptive measurement hardware and usable CAD-based measurement software have yet to be fully implemented in the manufacturing industry.
More recently, advances have been made in adaptive measurement hardware, as described in U.S. Pat. No. 5,402,582, the contents of which are incorporated herein by reference. Such hardware allows the measurement of points on an object and the comparison of the location of those points to CAD specifications. In order to speed the overall comparison process, the hardware should be connected to a local computer. Alternatively, as described in U.S. Pat. No. 5,978,748, the contents of which are also incorporated herein by reference, the hardware can be equipped with an on-board computer. Such systems allow precision measurement of assemblies at every step of the manufacturing process and at any location. Earlier systems required the assembly being measured to be taken to the confines of a quality control lab, which is time consuming and often impractical.
FIG. 1 is a diagrammatic view of a conventional three dimensional measuring system generally including a coordinate measuring system generally including a coordinate measuring machine (CCM) 10 composed of a manually operated multi-jointed arm 12 and a support base or post 14, a controller or serial box 16 and a host computer 18.
One significant drawback of the current state of technology referred to above is that CAD files demand powerful computers. Thus, the CAM2 market is limited by the power of the computers generally found and distributed in an affordable way to that market. It may be common for a company to have one or two powerful and expensive computers in its quality control lab, but unlikely for that same company to have numerous expensive computers distributed throughout a factory. Since the adaptive measurement hardware devices mentioned above typically are standalone stations assigned at different points in the manufacturing process, cost is a primary concern. Hence, the requirement to handle the CAD files becomes a limiting factor. Typical PC capabilities must be sufficient to handle large computer files, which are ordinarily handled by much more powerful workstations.
Many manufactured products today are highly curved in three-dimensions. Quality control inspections of such products requires the ability to measure points on the object's surface and compare them to the surfaces in the CAD file. CAD files are usually quite large since they contain information regarding these curves, and points, vectors, various layer settings and other features and information important to each particular CAD format and yet not always relevant to measurement.
Further, when comparing measurements on an assembly the user must select a surface on the CAD model from which to make that comparison. Very often, due to the complexity of the numerous surfaces contained in a CAD model, the basic act of selecting a surface can be difficult and time intensive. A single CAD model could contain hundreds or thousands of surfaces from which to choose. Even if the user narrows his or her search to a specific region of the model, those surfaces can sometimes be difficult to distinguish because they overlap, are small, or are grouped closely.